Naval designers already had access to larger calibres, including thirteen-, fourteen-, fifteen-, sixteen-, and eighteen-inch weapons. The twelve-inch choice was therefore deliberate rather than a limit imposed by the absence of heavier guns. It combined useful range and hitting power with a rate of fire and accuracy the ship could exploit. Dreadnought's armament illustrates why the best-performing naval gun for a design need not be the gun with the largest bore.
Notable Point · 4:59-5:36
Why Dreadnought balanced on twelve-inch guns
The twelve-inch gun offered HMS Dreadnought a practical balance of range, hitting power, rate of fire, and accuracy.